1. Field of the Invention
The present invention relates to a damping structure used for a portion required to prevent vibration noise, or a portion required to prevent noise by insulation from a sound source.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 7-164584 discloses a trussed damping structural material comprising two face plates and inclined ribs for connecting the face plates, wherein a damping resin is attached to either or both of the ribs and the face plates. Since the damping structural material is trussed, it has high cross section rigidity, and can thus increase a sound insulating effect when the damping resin is attached. Therefore, the damping structural material is suitable as a transport structure for, for example, railroad vehicles, or the like.
In the trussed structure disclosed in the above publication, as shown in FIGS. 17a, 17b and 17c, triangular holes are defined by two adjacent ribs and face plates. When deformation of one of the face plates transmits to the other face plate through the ribs, deformations of the two ribs are combined at the apex of each of triangles, and thus loads are applied to the face plates through the ribs in the normal direction, i.e., perpendicularly to the face plates, to push up the face plates (refer to an arrow in the drawing), thereby increasing vibration transmission. Also, the trussed structure has high rigidity and low cross section deformation to increase this phenomenon.
Since the trussed structure causes less cross section deformation, a damping material 5 attached to each of the ribs and the face plates is less distorted. The damping effect cannot be effectively exhibited unless the frequency is in a region in which the ribs and the face plates are deformed independently.
The present invention has been achieved in consideration of the above problems. An object of the present invention is to obtain a damping structure comprising a structure main body having a structure which less transmits vibration, and effectively exhibiting a damping function when damping treatment is performed with a damping material, and capable of securing necessary cross section rigidity. Another object of the present invention is to provide a shape and structure for effectively exhibiting the sound insulating effect of a structure body.
A damping structure according to the present invention is a double-walled damping structure comprising two parallel face plates; and a plurality of ribs extending in the same direction to connect said two parallel face plates, wherein in a section taken perpendicularly to the direction of extension of said ribs, all or most of holes defined by the surfaces of the adjacent two of said ribs and the inner surfaces of said face plates are quadrangular.
In the double-walled damping structure according to the present invention, less vibration is transmitted, because deformations of plural of the ribs are not combined at the junction of the rib and the face plate. Thus the damping function is effectively exhibited when damping treatment is performed, thereby more preventing vibration noise than a conventional example.
In the double-walled damping structure according to one aspect of the present invention, all or most of said ribs are inclined relative to said two face plates, and in a section taken perpendicularly to the direction of extension of said ribs, all or most of holes defined by the surfaces of the adjacent two of said ribs and the inner surfaces of said face plates are trapezoidal.
The holes defined by the adjacent two ribs and one of the face plates are triangular, and the holes defined by two adjacent ribs and both face plates are trapezoidal. In each of the trapezoidal holes, a space is formed between the junctions of each of the ribs and one of the face plates. In the present invention, xe2x80x9cmostxe2x80x9d means a xe2x80x9cmajorityxe2x80x9d.
In the double-walled damping structure described above, less vibration is transmitted, and furthermore, cross section rigidity as a structure can be secured.
In the double-walled damping structure described above, when a plurality of triangular holes defined by the surfaces of the adjacent two of said ribs and the inner surfaces of said face plates are present other than the trapezoidal holes in a section taken perpendicularly to the direction of extension of said ribs, all of the inner surfaces of the triangular holes are preferably included in only one of said face plates.
In the double-walled damping structure described above, in a section taken perpendicularly to the direction of extension of said ribs, when a plurality of triangular holes defined by the surfaces of the adjacent two of said ribs and the inner surfaces of said face plates are present other than the trapezoidal, the trapezoidal holes are preferably present between the respective triangular holes.
In the double-walled damping structure described above, in a section taken perpendicularly to the direction of extension of said ribs, triangular may be defined by the surfaces of the adjacent two of said ribs and the inner surfaces of said face plates only at both ends in the width direction.
By combining a plurality of the above-described double-walled damping structures as units in the width direction, it is possible to form a wide double-walled damping structure comprising two parallel face plates, and a plurality of ribs extending in the same direction, for connecting the two face plates.
A damping material may be attached to either or both of the face plates and the ribs, or the hollows between the face plates may be filled with a damping material such as a damping resin foam material or the like according to demand.
The double-walled damping structure may be an extruded product of aluminum or an aluminum alloy, or a molded product of a resin or mainly composed of a resin.
The double-walled damping structure according to another aspect of the present invention is a double-walled sound insulation structure comprising two parallel face plates having a same thickness, and a plurality of vertical ribs extending in parallel with a substantially equal pitch to connect the two parallel face plates.
In the double-walled damping structure described above, assuming that the Young""s modulus, density and thickness of each of the face plates are E, xcfx81, and t, respectively, and the pitch of the ribs is 1, the following equation (1) is preferably satisfied:                               250          ≤                                                    k                2                                            4                ⁢                π                                      ·                          t                              l                2                                      ·                                          (                                                      E                    /                    3                                    ⁢                  ρ                                )                                            1                /                2                                              ≤          5000                ⁢                  
                ⁢                                            (wherein                        ⁢                          xe2x80x83                        ⁢            k                    =                      4.72            ⁢                          )                                                          (        1        )            
In the structure, the acoustic radiation can be decreased efficiently due to the occurrence of cancellation in a radiated acoustic wave, thereby obtaining a high sound insulating effect.